Astrologically 8th house is called the paataal, and therefore whenever any benefic planets will go to the 8th house it will get weak and loses out on its benefic aspects. Of course never predictions should be made based upon one aspect alone in astrology, you should look at the complete chart. There will always be aspects / conjunctions of other planets that also play a very important role in prediction. However only taking your question of 2nd / 5th and 9th house in 8th house will generally give malefic effects.
Blessings,
Navneet Khanna
Astrologer